The areas in a winter cover which are most vulnerable to water intrusion and damage are the standing rigging penetrations. The total number of penetrations will of course, impact your method choices for covering.
After considerable research, I had ambitions to fabricate a reusable cover using a cotton/synthetic fabric blend. The plan was to accommodate two masts with up to 14-16 shroud and stay penetrations, utilizing a combination of zippers, laced lashings with sewn flaps and fabric boots.
I constructed the metal frame
using EMT and specialized clamps, but have been vacillating over the fabric phase - due to the complexity involved with these penetrations and the time involved to make this thing.
So, this will be the third winter I simply call the shrinkwrap guys to cover the frame. The material cost for the frame was $200 and shrinkwrapping charges for my 36 ft LOA ketch has risen in 3 years from $330 to $400 - (cheap). So, the total expense for covering (frame included) for 3 years will be about $1,300.
In contrast, I received an estimate for a custom fabric cover from Fairclough for over $5,000. Material and accessories to make the fabric cover myself would have been roughly $800 - plus many hours of labor and frustration - assuming my sewing machine is capable - otherwise the 600. cost of a new Sailrite machine would need to be factored in.
Of course, if you choose to unstep the masts each winter, the cover cost will be considerably less by the use of a simple tarp - but seasonal stepping and unstepping rigging fees will offset the savings.
I hope this information was helpful and if you'd like more details, please let me know.